Hibernate using multiple databases

Question

Someone know how to add a another datasource in hibernate configuration and how to configure Spring to that datasource its autoinject in my respective DAO?

This is m

Answer 1

I'll add my example too. Maybe it will be usefull for another situations like getting data from one database and writing it to another with EntityManager.

So my applicationContext.xml:

Package business.domain has entity classes for remote connection.

Package local.business.domain has entities for local connection.

Entities have annotation mappings for columns and relations.

Then 2 DAO classes:

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

@Repository
public class RemoteDao {

  @PersistenceContext(unitName="unitRemote")
  protected EntityManager em;

  // ...

}

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

@Repository
@Transactional(value="transactionManagerLocal")
public class LocalDao {

  @PersistenceContext(unitName="unitLocal")
  protected EntityManager em;

  // ...

}

With this I could use @Autowired to inject DAOs in my JUnit test:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "/config/applicationContext.xml" })
public class DaoTest {

  @Autowired
  private RemoteDao remoteDao;

  @Autowired
  private LocalDao localDao;


  @Test
  public void daoTest(){
    Entity entity = remoteDao.find(id);
    localDao.persist(entity);
  }

}

So here it's possible to use DAOs without service if this is needed for simple applications, tests or DB migration scripts.